In medical diagnosis applications, one important issue is the generation of images of a patient based on the detection of ionizing radiation. In this context, various imaging methods and systems exist, such as computed tomography (CT), positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Such imaging systems make use of detection modules that allow the generation of images based on detected radiation. A detection module therefor usually comprises a scintillation detector (sometimes also referred to as scintillator), in particular a scintillator crystal or an array of scintillator crystals, and a photosensor (sometimes also referred to as photodetector). The scintillator scintillates, i.e. emits light flashes (scintillation photons), in response to incoming ionizing radiation (i.e. impinging particles such as electrons, alpha particles, ions or high-energy photons etc.). The emitted photons are captured by the photosensor. Based on where, when and which number of scintillation photons is captured the temporal and spatial position and/or intensity of the incident ionizing radiation on the scintillation detector can be determined. It then becomes possible to generate an image of an object or imaging subject interacting with the ionizing radiation.
One technique thereby relates to generating an image corresponding to the intensity of the captured ionizing radiation. One difficulty with energy-resolved imaging is a possibly high-energy bandwidth of the incident ionizing radiation. In the context of CT imaging, the development of the double decker technology is one option to solve the problem of energy-resolved CT imaging. Other technologies are, e.g., counting detectors. Such a double decker detector may use a stack of, e.g., two scintillator crystals mounted on top of each other. The detection of the emitted scintillation light may then be accomplished by a double-photodiode (photosensor) mounted at the side of one pixel (two scintillator crystals). Each of the two photodiodes is intended to collect the light of the adjacent scintillator element.
In WO 2012/127403 A2, a method that includes obtaining a photosensor substrate having two opposing major surfaces is disclosed. One of the two opposing major surfaces includes at least one photosensor row of at least one photosensor element, and the obtained photosensor substrate has a thickness equal to or greater than one hundred microns. The method further includes optically coupling a scintillator array to the photosensor substrate. The scintillator array includes at least one complementary scintillator row of at least one complementary scintillator element, and the at least one complementary scintillator row is optically coupled to the at least one photosensor row and the at least one complementary scintillator element is optically coupled to the at least one photosensor element. The method further includes thinning the photosensor substrate optically coupled to the scintillator producing a thinned photosensor substrate that is optically coupled to the scintillator and that has a thickness on the order of less than one hundred microns.
US 2013/0292574 A1 discloses an imaging system including a radiation sensitive detector array. A scintillator array layermay be provided on a photosensor array layer including a two-dimensional array of photodiodes mounted on a substrate. It is reported that a photodiode may be mounted directly on a film, such as a plastic or polyamide sheet. Alternatively, a thin photodiode array may be printed on a flexible plastic sheet.
US 2008/0011960 A1 pertains to a radiographic imaging apparatus having two panels, each of them including a substrate, an array of signal sensing elements and readout devices, a passivation layer and a scintillating phosphor layer.
WO 2007/039840 A2 refers to an X-ray detector array having a number of detector elements. Each detector element includes a scintillator, a photodetector optically coupled to the scintillator and a circuit board. The circuit board may be a flexible circuit including a polymer substrate. One problem of such detectors is, however, that the efficiency, i.e. the light collection efficiency, may be limited due to the limited area of the photosensor being in contact with the scintillator elements. A possible compensation for this includes the application of a suitable reflecting material at the other side of the crystal, which has a disadvantage with respect to material and assembly costs. Furthermore, the area sensitive to ionizing radiation may be reduced. Still further, the optical crosstalk (i.e. detecting scintillation photons emitted by one scintillator element with another photosensitive element than intended for the readout of this scintillator element) resulting from optically coupling the photosensor to the vertical scintillator stack and also the packaging and connection of the photosensor to the tile substrate may result in a more expensive advanced packaging process.